﻿172 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  194 
  3 
  

  

  organic 
  matter 
  consists 
  of 
  about 
  60 
  percent 
  carbon, 
  7 
  percent 
  nitrogen, 
  

   and 
  the 
  remainder 
  chiefly 
  hydrogen. 
  In 
  ancient 
  sediments 
  the 
  pro- 
  

   portion 
  of 
  nitrogen 
  increases, 
  indicating 
  that 
  there 
  has 
  been 
  loss 
  of 
  

   hydrogen 
  and 
  carbon 
  through 
  geologic 
  change 
  (Trask, 
  1932, 
  p. 
  222). 
  

   Dark 
  sediments 
  generally 
  have 
  a 
  higher 
  organic 
  content 
  than 
  lighter 
  

   ones, 
  and 
  the 
  blackness 
  of 
  many 
  marine 
  shales 
  is 
  chiefly 
  due 
  to 
  con- 
  

   tained 
  organic 
  matter 
  (Twenhofel, 
  1939, 
  p. 
  1181) 
  . 
  Hence, 
  dark 
  marine 
  

   shales 
  are 
  generally 
  regarded 
  as 
  good 
  source 
  beds 
  and, 
  when 
  near 
  oil 
  

   reservoirs, 
  are 
  considered 
  as 
  the 
  most 
  probable 
  source 
  of 
  the 
  petroleum 
  

   (Snider, 
  1934, 
  p. 
  62). 
  

  

  The 
  organic 
  matter 
  in 
  recent 
  sediments 
  consists 
  of 
  a 
  highly 
  complex 
  

   group 
  of 
  substances 
  (Trask, 
  1932, 
  p. 
  198). 
  Oils 
  and 
  fats 
  constitute 
  

   only 
  1 
  percent; 
  waxes, 
  resins, 
  alkaloids, 
  and 
  alcohols 
  comprise 
  about 
  

   5 
  percent; 
  carbohydrates 
  form 
  less 
  than 
  1 
  percent; 
  sugars, 
  starches, 
  

   and 
  other 
  water-soluble 
  substances, 
  chiefly 
  organic 
  acids, 
  form 
  3 
  

   percent. 
  Nitrogenous 
  compounds 
  form 
  the 
  largest 
  group, 
  comprising 
  

   about 
  40 
  percent, 
  about 
  half 
  being 
  proteins 
  and 
  the 
  remainder 
  more 
  

   resistant 
  nitrogenous 
  compounds. 
  Finally, 
  about 
  30 
  percent 
  of 
  the 
  

   organic 
  matter 
  consists 
  of 
  lignins 
  and 
  humic 
  complexes. 
  It 
  is 
  from 
  

   such 
  source 
  materials 
  that 
  hydrocarbons 
  must 
  have 
  been 
  derived. 
  

  

  The 
  organic 
  matter 
  of 
  recent 
  sediments 
  is 
  nearly 
  all 
  present 
  in 
  solid 
  

   form. 
  The 
  proportion 
  soluble 
  in 
  hot 
  water 
  comprises 
  only 
  about 
  

   3 
  percent, 
  and 
  all 
  the 
  material 
  extracted 
  from 
  such 
  sediments 
  by 
  solu- 
  

   tion 
  in 
  carbon 
  tetrachloride 
  appears 
  to 
  be 
  solid 
  in 
  nature 
  (Trask, 
  

   1932, 
  p. 
  173). 
  

  

  CONVERSION 
  OF 
  ORGANIC 
  MATTER 
  TO 
  PETROLEUM 
  

  

  The 
  problem 
  of 
  when, 
  where, 
  and 
  how 
  the 
  organic 
  content 
  of 
  sedi- 
  

   ments 
  was 
  converted 
  into 
  petroleum 
  is 
  a 
  refinement 
  to 
  which 
  the 
  geolo- 
  

   gist 
  of 
  half 
  a 
  century 
  ago 
  had 
  not 
  advanced 
  and 
  which 
  received 
  very 
  

   little 
  attention 
  until 
  20 
  years 
  ago. 
  From 
  the 
  time 
  that 
  the 
  problem 
  

   assumed 
  definite 
  form, 
  geologists 
  have 
  been 
  primarily 
  concerned 
  

   with 
  the 
  time 
  and 
  place 
  of 
  conversion, 
  while 
  the 
  manner 
  in 
  which 
  the 
  

   change 
  occurred 
  has 
  been 
  left 
  largely 
  to 
  the 
  chemists 
  and 
  biologists. 
  

  

  The 
  uppermost 
  layers 
  of 
  newly 
  deposited 
  sediments 
  have 
  a 
  dense 
  

   bacterial 
  population, 
  and 
  such 
  microorganisms 
  are 
  probably 
  an 
  im- 
  

   portant 
  factor 
  in 
  the 
  generation 
  of 
  hydrocarbons. 
  Bacteria 
  func- 
  

   tion 
  to 
  remove 
  nitrogen 
  and 
  oxygen 
  from 
  the 
  organic 
  matter 
  con- 
  

   tained 
  in 
  the 
  sediments, 
  which 
  is 
  thus 
  changed 
  in 
  composition 
  so 
  as 
  

   more 
  nearly 
  to 
  resemble 
  petroleum 
  (Hammar, 
  1934). 
  This 
  trans- 
  

   formation 
  probably 
  occurs 
  very 
  early 
  in 
  the 
  history 
  of 
  the 
  sediments, 
  

   and 
  there 
  is 
  little 
  if 
  any 
  evidence 
  to 
  support 
  the 
  view 
  that 
  bacterial 
  

   action 
  continues 
  after 
  sediments 
  have 
  been 
  deeply 
  buried 
  and 
  subjected 
  

   to 
  dynamic 
  action 
  (David 
  White, 
  1935). 
  

  

  